In the field of high-speed printing devices which are especially suitable for use in connection with electronic data processing systems, the wire matrix type of printer has come into increasing use. In this type of printer, letters, numbers and symbols are formed from a series of dots produced by the impact of the head of a plurality of wire elements on a record media. Interposed between the wire elements and the record media customarily is an ink ribbon which provides the ink needed to produce a mark on the record medium being printed upon. In addition, in the past the number of wires has generally been restricted to the range of seven through nine. As the art advances, an obvious need for increased numbers of wires, for example 18 wires, arises so that variation of symbols and better quality of letters and numbers may be printed.
One problem which has arisen in connection with the use of wire printers is that of fatigue breakage of the print wires which breakage is caused by the bending and vibration of the print wires under the high force employed to drive the wires over a short distance to impact upon the record medium. This vibration may be in a multimode direction, that is transverse to the length of the wire. In order to reduce or eliminate such breakage in some prior art structures the individual print wires have been confined within print head blocks or units, or within tubes or coil springs anchored in the printer framework. These structures have the disadvantages of increasing the parts and labor costs, and also tend to impede the movement of the printer wires by frictional engagement between the wires and the tubes. In U.S. Pat. No. 4,081,067 entitled "Internal Vibration Dampening Means For Printing Mechanism" by R. L. Schrag et al. there is disclosed a wire dampening mechanism formed as a conical elongated unit inserted into the central area of the wire print head with the wires positioned around the periphery thereof. Wire bending is thus restricted when the wire deflects sufficiently to come into contact with the outer surface of the conical element.
Another prior art device of interest is disclosed in U.S. Pat. No. 3,897,865 entitled "Dot Printing Apparatus" by D. P. Darwin et al. The wire print head disclosed in that patent is comprised of an inner central cone having longitudinal slots along the outer surface thereof to receive and guide the print wires and a second cone positioned over the first inner cone to encase the inner cone and the wires. The wires of the print head thus have a continuous guide support for each individual wire from the input to a point at which they are positioned parallel and nearly colinear at the output end of the printer. Two features claimed for the print head are (1) that the print head is easier to construct, and (2) that the paths of the individual wires are equal and that the ends of the wires are parallel at the output instead of convergent.
Another patent of interest is U.S. Pat. No. 4,004,671 entitled "Wire Matrix Print Head" by N. Kondur, Jr. In the print head of the reference there is provided a generally conical, slotted wire guide body which converges forwardly into a hollow head and terminates in a bearing portion at its leading end. The bearing portion defines a series of vertically aligned, closely spaced openings for reception of the leading ends of the print wires. The slots in the conical body generally conform in width to the diameter of the cross-sectional size of a print wire. Each slot varies in depth along its length, and each slot is of a slightly different depth to permit its respective print wire to be disposed to extend along its elastic curve.